Manufacture of foundry molds



jlqp'li bliuoo ncrizncliui: wimmm rim Jan. 17, 1939 2,144,532

UNITED STATES PATENT OFFICE wesaitinmtionnlatestothemanuerlbletomeanamountotwatermtially and.more epeoisiiy. lelsthanthatemployedinmahingihemusiceor ulatedthstwhenthecement-sandmixtureis corehoxtotormaiacinglayerotahoutkto emu to %otan*inchthick. 'niisiacinglayermaybe form a highly friable ball. This mixture can employed over the entire face 01 the mold cavhemoldedortampedtoiormamold orcoreoi' ltmormaybeemlilor ylt min l where it relatively high porosity and good ltructurai trouble would otherwise be encountered oi the The Durand process has gone into molten metal penetra ing into he mold maratherextensiveuseandhasmadeadistinct terial. Thetermtacing"lsusedintheclaim improvement in foundry practice. Dimeult is n d o in lude f ing which may cover high temperature; where the casting has reprovide a good bond with the cement-sand mixsand by the metal, forming at the bottom of the ment-sand mold re-entrant angle a porous mass consisting of a The mold box is taken on the mold. which is conglomerate of metal and partially fused sand allowed to set as in the reaular Durand process. 30

which is exceedingly resistant to removal by cutand which is then ready for use. ting. arinding, or chipp ir. This action is ap- Ihe completed mold consists of a porous backparently due to a combination oi physical and log formed oi the relatively dry or "sub-hymust be porous to allow the escape od Bases highly refractory racing, which may be or con- 40 tionotthemetalandtendstoformtheintensely the lacing to separate from the backing. The 40 vantages may be entirely overcome by providing orsteel or other highly heated metal into the 5 of substantial thickness composed or M the regular Durand mix, has the high porosity the lines of the fused alumina employed for mold. n 180 as e Structural i h reabrasive purposes. This material is sold me: '1 various trade names. such as the well known The 1118111! fused m md I the tendency to form a glass with the cement. so used the imamfiunu m m which encountered with the #111 with good mum, in pram Wm While a limited amount 01' wateris used to retain eomeporosityintheiacinglayenthennegnin the m M oi. the aluminum oxide fines :ives a close trained 5 Alumna 1m structure to the facing which resists penetration cementu orthemetalandwhichgivesasmoothlurtaee wlter 7 to the casting whiierpi-e'rertoueethenaeuuimnimnnes While the water contentmsy be somewhatmore from abrasive manufacture, coarser drained aluw thanthatoithetypicalDlu-andmmithprdminsmaybeuseditdedredmithoughitisusuau e0 green or drysand, clnders. or the like.

The fadng layer consists alumina and may. if desired. contain minor amounts of other sands. but not sufficient however to materially affect the refractory properties of the mixture.

The material used for a binder is preferably high early strength Portland cement, although ordinary Portland cement or r may be used The term foundry mold as used in the claims is intended to include cores as well as molds.

While I have described a preferred embodiment of my invention and have described paraucsaa tieularmaterialswhichmaybeutiliseditwillbe thatmyinventlonmaybe practiced or embodiedwithintheseopeoftne of substantial thickness composed principally of nnelydivlded fused m m bondedwith cemen,anda integrallynnitedwiththe facing and composed principally of ordinary sand bonded with cement and having a high porosity.

2. A foundry mold comprising a facing of substantial thickness composed principally of granular refractory aluminum oxide bonded with cement, and a porous backing composed principally of sand and cement integrally united with the facing.

3. A foundry mold comprising a facing formed from a moldable but friable mix consisting principally of granular alumina and cement together with an amount of water insufficient to form a dense mixture, and a backing formed from a moldable but friable mixture of sand and cement containing so little water as to form a mass of high porosity.

4. A foundry mold having a facing consisting principally of granular refractory alumina bonded with cement.

JOHN HOW! HALL. 

